The Obama administration said Tuesday that it is preparing a major relief effort for Sri Lanka amid expections that the nation's 26-year civil war will end within days - at a cost of tens of thousands of civilian lives. (...)

Mr. Owen said the administration has urged both sides to show restraint and protect the civilians caught in the fighting. The U.S. government estimates that 125,000 civilians were trapped in the "no-fire zone" in the Tamil Tigers' northern stronghold until Monday, when about 35,000 fled after government forces broke through a key line of defense, Mr. Owen said.

Another 25,000 escaped Tuesday, he said, leaving about 65,000 still in harm's way. He said the U.S. government is identifying available resources to aid victims of the conflict after the fighting stops. At a human rights hearing on Capitol Hill, lawmakers said they were concerned at the inability of aid workers and journalists to enter the conflict zone.

"In my experience, whenever journalists - let alone journalists and humanitarian workers - are deliberately kept from getting to and reporting on conflicts and crises, you can bet that something is going on that cannot stand up to the light of day," said Rep. James McGovern, Massachusetts Democrat.

Mr. McGovern and other lawmakers stressed an international responsibility to protect civilians in the region, regardless of which side they are on. "Right now, it doesn't seem that there are good actors with whom to align when it comes to the plight of the civilian population caught in the conflict zone," said Rep. Donna Edwards, Maryland Democrat.

Humanitarian groups say the government has killed scores of civilians by shelling no-fire zones, while rebels continue to use civilians as human shields - charges both sides deny. "However horrific this situation is, it is about to become much worse. Fears are that the civilians remaining in the zone ... will be considered fair game leading to a mass slaughter, in the government's final assault against the insurgents," said Sarah Holewinski, director of Campaign for Innocent Victims in Conflict. (...)

Overall, more than 70,000 people have been killed since the LTTE began its insurgency in 1983 to carve out an independent homeland for the ethnic minority Tamils, who have been marginalized by ethnic Sinhalese-dominated governments. A 24-hour ultimatum, issued Monday, demanded that all militants lay down their weapons by noon Tuesday and that Tamil Tiger rebel chief Velupillai Prabhakaran turn himself in to authorities. The deadline passed with no reply from LTTE spokespeople or affiliated media outlets.

However, in an apparent signal of vulnerability, a statement from the movement's political wing was posted on the pro-rebel Web site shortly after the military's breakthrough Monday, calling for a cease-fire without preconditions.